Conventionally, a Fabry-Perot type variable spectroscopy device which varies the wavelength of transmission light by changing a surface interval between two planar optical substrates is known (e.g., refer to Patent Document 1).
The variable spectroscopy device includes a reflection film and a capacitance sensor electrode on the opposing surface of each optical substrate. The variable spectroscopy device can detect the size of the interval between the optical substrates using the capacitance value between the capacitance sensor electrodes and make fine adjustments of the surface interval by controlling the driving voltage of an actuator.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2002-277758